diff options
Diffstat (limited to 'src/dmarc.c')
| -rw-r--r-- | src/dmarc.c | 612 |
1 files changed, 612 insertions, 0 deletions
diff --git a/src/dmarc.c b/src/dmarc.c new file mode 100644 index 0000000..f29f7eb --- /dev/null +++ b/src/dmarc.c @@ -0,0 +1,612 @@ +/************************************************* +* Exim - an Internet mail transport agent * +*************************************************/ +/* Experimental DMARC support. + Copyright (c) Todd Lyons <tlyons@exim.org> 2012 - 2014 + License: GPL */ + +/* Portions Copyright (c) 2012, 2013, The Trusted Domain Project; + All rights reserved, licensed for use per LICENSE.opendmarc. */ + +/* Code for calling dmarc checks via libopendmarc. Called from acl.c. */ + +#include "exim.h" +#ifdef EXPERIMENTAL_DMARC +# if !defined SUPPORT_SPF +# error SPF must also be enabled for DMARC +# elif defined DISABLE_DKIM +# error DKIM must also be enabled for DMARC +# else + +# include "functions.h" +# include "dmarc.h" +# include "pdkim/pdkim.h" + +OPENDMARC_LIB_T dmarc_ctx; +DMARC_POLICY_T *dmarc_pctx = NULL; +OPENDMARC_STATUS_T libdm_status, action, dmarc_policy; +OPENDMARC_STATUS_T da, sa, action; +BOOL dmarc_abort = FALSE; +uschar *dmarc_pass_fail = US"skipped"; +header_line *from_header = NULL; +extern SPF_response_t *spf_response; +int dmarc_spf_ares_result = 0; +uschar *spf_sender_domain = NULL; +uschar *spf_human_readable = NULL; +u_char *header_from_sender = NULL; +int history_file_status = DMARC_HIST_OK; +uschar *dkim_history_buffer= NULL; + +typedef struct dmarc_exim_p { + uschar *name; + int value; +} dmarc_exim_p; + +static dmarc_exim_p dmarc_policy_description[] = { + /* name value */ + { US"", DMARC_RECORD_P_UNSPECIFIED }, + { US"none", DMARC_RECORD_P_NONE }, + { US"quarantine", DMARC_RECORD_P_QUARANTINE }, + { US"reject", DMARC_RECORD_P_REJECT }, + { NULL, 0 } +}; +/* Accept an error_block struct, initialize if empty, parse to the + * end, and append the two strings passed to it. Used for adding + * variable amounts of value:pair data to the forensic emails. */ + +static error_block * +add_to_eblock(error_block *eblock, uschar *t1, uschar *t2) +{ +error_block *eb = store_malloc(sizeof(error_block)); +if (eblock == NULL) + eblock = eb; +else + { + /* Find the end of the eblock struct and point it at eb */ + error_block *tmp = eblock; + while(tmp->next != NULL) + tmp = tmp->next; + tmp->next = eb; + } +eb->text1 = t1; +eb->text2 = t2; +eb->next = NULL; +return eblock; +} + +/* dmarc_init sets up a context that can be re-used for several + messages on the same SMTP connection (that come from the + same host with the same HELO string) */ + +int +dmarc_init() +{ +int *netmask = NULL; /* Ignored */ +int is_ipv6 = 0; + +/* Set some sane defaults. Also clears previous results when + * multiple messages in one connection. */ +dmarc_pctx = NULL; +dmarc_status = US"none"; +dmarc_abort = FALSE; +dmarc_pass_fail = US"skipped"; +dmarc_used_domain = US""; +f.dmarc_has_been_checked = FALSE; +header_from_sender = NULL; +spf_sender_domain = NULL; +spf_human_readable = NULL; + +/* ACLs have "control=dmarc_disable_verify" */ +if (f.dmarc_disable_verify == TRUE) + return OK; + +(void) memset(&dmarc_ctx, '\0', sizeof dmarc_ctx); +dmarc_ctx.nscount = 0; +libdm_status = opendmarc_policy_library_init(&dmarc_ctx); +if (libdm_status != DMARC_PARSE_OKAY) + { + log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure to init library: %s", + opendmarc_policy_status_to_str(libdm_status)); + dmarc_abort = TRUE; + } +if (!dmarc_tld_file) + { + DEBUG(D_receive) debug_printf("DMARC: no dmarc_tld_file\n"); + dmarc_abort = TRUE; + } +else if (opendmarc_tld_read_file(CS dmarc_tld_file, NULL, NULL, NULL)) + { + log_write(0, LOG_MAIN|LOG_PANIC, "DMARC failure to load tld list %s: %d", + dmarc_tld_file, errno); + dmarc_abort = TRUE; + } +if (!sender_host_address) + { + DEBUG(D_receive) debug_printf("DMARC: no sender_host_address\n"); + dmarc_abort = TRUE; + } +/* This catches locally originated email and startup errors above. */ +if (!dmarc_abort) + { + is_ipv6 = string_is_ip_address(sender_host_address, netmask) == 6; + if (!(dmarc_pctx = opendmarc_policy_connect_init(sender_host_address, is_ipv6))) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "DMARC failure creating policy context: ip=%s", sender_host_address); + dmarc_abort = TRUE; + } + } + +return OK; +} + + +/* dmarc_store_data stores the header data so that subsequent +dmarc_process can access the data */ + +int +dmarc_store_data(header_line *hdr) +{ +/* No debug output because would change every test debug output */ +if (!f.dmarc_disable_verify) + from_header = hdr; +return OK; +} + + +static void +dmarc_send_forensic_report(u_char **ruf) +{ +int c; +uschar *recipient, *save_sender; +BOOL send_status = FALSE; +error_block *eblock = NULL; +FILE *message_file = NULL; + +/* Earlier ACL does not have *required* control=dmarc_enable_forensic */ +if (!f.dmarc_enable_forensic) + return; + +if ( dmarc_policy == DMARC_POLICY_REJECT && action == DMARC_RESULT_REJECT + || dmarc_policy == DMARC_POLICY_QUARANTINE && action == DMARC_RESULT_QUARANTINE + || dmarc_policy == DMARC_POLICY_NONE && action == DMARC_RESULT_REJECT + || dmarc_policy == DMARC_POLICY_NONE && action == DMARC_RESULT_QUARANTINE + ) + if (ruf) + { + eblock = add_to_eblock(eblock, US"Sender Domain", dmarc_used_domain); + eblock = add_to_eblock(eblock, US"Sender IP Address", sender_host_address); + eblock = add_to_eblock(eblock, US"Received Date", tod_stamp(tod_full)); + eblock = add_to_eblock(eblock, US"SPF Alignment", + sa == DMARC_POLICY_SPF_ALIGNMENT_PASS ? US"yes" : US"no"); + eblock = add_to_eblock(eblock, US"DKIM Alignment", + da == DMARC_POLICY_DKIM_ALIGNMENT_PASS ? US"yes" : US"no"); + eblock = add_to_eblock(eblock, US"DMARC Results", dmarc_status_text); + + for (c = 0; ruf[c]; c++) + { + recipient = string_copylc(ruf[c]); + if (Ustrncmp(recipient, "mailto:",7)) + continue; + /* Move to first character past the colon */ + recipient += 7; + DEBUG(D_receive) + debug_printf("DMARC forensic report to %s%s\n", recipient, + (host_checking || f.running_in_test_harness) ? " (not really)" : ""); + if (host_checking || f.running_in_test_harness) + continue; + + if (!moan_send_message(recipient, ERRMESS_DMARC_FORENSIC, eblock, + header_list, message_file, NULL)) + log_write(0, LOG_MAIN|LOG_PANIC, + "failure to send DMARC forensic report to %s", recipient); + } + } +} + +/* dmarc_process adds the envelope sender address to the existing +context (if any), retrieves the result, sets up expansion +strings and evaluates the condition outcome. */ + +int +dmarc_process() +{ +int sr, origin; /* used in SPF section */ +int dmarc_spf_result = 0; /* stores spf into dmarc conn ctx */ +int tmp_ans, c; +pdkim_signature * sig = dkim_signatures; +BOOL has_dmarc_record = TRUE; +u_char **ruf; /* forensic report addressees, if called for */ + +/* ACLs have "control=dmarc_disable_verify" */ +if (f.dmarc_disable_verify) + return OK; + +/* Store the header From: sender domain for this part of DMARC. + * If there is no from_header struct, then it's likely this message + * is locally generated and relying on fixups to add it. Just skip + * the entire DMARC system if we can't find a From: header....or if + * there was a previous error. + */ +if (!from_header) + { + DEBUG(D_receive) debug_printf("DMARC: no From: header\n"); + dmarc_abort = TRUE; + } +else if (!dmarc_abort) + { + uschar * errormsg; + int dummy, domain; + uschar * p; + uschar saveend; + + f.parse_allow_group = TRUE; + p = parse_find_address_end(from_header->text, FALSE); + saveend = *p; *p = '\0'; + if ((header_from_sender = parse_extract_address(from_header->text, &errormsg, + &dummy, &dummy, &domain, FALSE))) + header_from_sender += domain; + *p = saveend; + + /* The opendmarc library extracts the domain from the email address, but + * only try to store it if it's not empty. Otherwise, skip out of DMARC. */ + if (!header_from_sender || (strcmp( CCS header_from_sender, "") == 0)) + dmarc_abort = TRUE; + libdm_status = dmarc_abort + ? DMARC_PARSE_OKAY + : opendmarc_policy_store_from_domain(dmarc_pctx, header_from_sender); + if (libdm_status != DMARC_PARSE_OKAY) + { + log_write(0, LOG_MAIN|LOG_PANIC, + "failure to store header From: in DMARC: %s, header was '%s'", + opendmarc_policy_status_to_str(libdm_status), from_header->text); + dmarc_abort = TRUE; + } + } + +/* Skip DMARC if connection is SMTP Auth. Temporarily, admin should + * instead do this in the ACLs. */ +if (!dmarc_abort && !sender_host_authenticated) + { + uschar * dmarc_domain; + + /* Use the envelope sender domain for this part of DMARC */ + spf_sender_domain = expand_string(US"$sender_address_domain"); + if (!spf_response) + { + /* No spf data means null envelope sender so generate a domain name + * from the sender_helo_name */ + if (!spf_sender_domain) + { + spf_sender_domain = sender_helo_name; + log_write(0, LOG_MAIN, "DMARC using synthesized SPF sender domain = %s\n", + spf_sender_domain); + DEBUG(D_receive) + debug_printf("DMARC using synthesized SPF sender domain = %s\n", + spf_sender_domain); + } + dmarc_spf_result = DMARC_POLICY_SPF_OUTCOME_NONE; + dmarc_spf_ares_result = ARES_RESULT_UNKNOWN; + origin = DMARC_POLICY_SPF_ORIGIN_HELO; + spf_human_readable = US""; + } + else + { + sr = spf_response->result; + dmarc_spf_result = sr == SPF_RESULT_NEUTRAL ? DMARC_POLICY_SPF_OUTCOME_NONE : + sr == SPF_RESULT_PASS ? DMARC_POLICY_SPF_OUTCOME_PASS : + sr == SPF_RESULT_FAIL ? DMARC_POLICY_SPF_OUTCOME_FAIL : + sr == SPF_RESULT_SOFTFAIL ? DMARC_POLICY_SPF_OUTCOME_TMPFAIL : + DMARC_POLICY_SPF_OUTCOME_NONE; + dmarc_spf_ares_result = sr == SPF_RESULT_NEUTRAL ? ARES_RESULT_NEUTRAL : + sr == SPF_RESULT_PASS ? ARES_RESULT_PASS : + sr == SPF_RESULT_FAIL ? ARES_RESULT_FAIL : + sr == SPF_RESULT_SOFTFAIL ? ARES_RESULT_SOFTFAIL : + sr == SPF_RESULT_NONE ? ARES_RESULT_NONE : + sr == SPF_RESULT_TEMPERROR ? ARES_RESULT_TEMPERROR : + sr == SPF_RESULT_PERMERROR ? ARES_RESULT_PERMERROR : + ARES_RESULT_UNKNOWN; + origin = DMARC_POLICY_SPF_ORIGIN_MAILFROM; + spf_human_readable = US spf_response->header_comment; + DEBUG(D_receive) + debug_printf("DMARC using SPF sender domain = %s\n", spf_sender_domain); + } + if (strcmp( CCS spf_sender_domain, "") == 0) + dmarc_abort = TRUE; + if (!dmarc_abort) + { + libdm_status = opendmarc_policy_store_spf(dmarc_pctx, spf_sender_domain, + dmarc_spf_result, origin, spf_human_readable); + if (libdm_status != DMARC_PARSE_OKAY) + log_write(0, LOG_MAIN|LOG_PANIC, "failure to store spf for DMARC: %s", + opendmarc_policy_status_to_str(libdm_status)); + } + + /* Now we cycle through the dkim signature results and put into + * the opendmarc context, further building the DMARC reply. */ + dkim_history_buffer = US""; + while (sig) + { + int dkim_result, dkim_ares_result, vs, ves; + + vs = sig->verify_status & ~PDKIM_VERIFY_POLICY; + ves = sig->verify_ext_status; + dkim_result = vs == PDKIM_VERIFY_PASS ? DMARC_POLICY_DKIM_OUTCOME_PASS : + vs == PDKIM_VERIFY_FAIL ? DMARC_POLICY_DKIM_OUTCOME_FAIL : + vs == PDKIM_VERIFY_INVALID ? DMARC_POLICY_DKIM_OUTCOME_TMPFAIL : + DMARC_POLICY_DKIM_OUTCOME_NONE; + libdm_status = opendmarc_policy_store_dkim(dmarc_pctx, US sig->domain, + dkim_result, US""); + DEBUG(D_receive) + debug_printf("DMARC adding DKIM sender domain = %s\n", sig->domain); + if (libdm_status != DMARC_PARSE_OKAY) + log_write(0, LOG_MAIN|LOG_PANIC, + "failure to store dkim (%s) for DMARC: %s", + sig->domain, opendmarc_policy_status_to_str(libdm_status)); + + dkim_ares_result = + vs == PDKIM_VERIFY_PASS ? ARES_RESULT_PASS : + vs == PDKIM_VERIFY_FAIL ? ARES_RESULT_FAIL : + vs == PDKIM_VERIFY_NONE ? ARES_RESULT_NONE : + vs == PDKIM_VERIFY_INVALID ? + ves == PDKIM_VERIFY_INVALID_PUBKEY_UNAVAILABLE ? ARES_RESULT_PERMERROR : + ves == PDKIM_VERIFY_INVALID_BUFFER_SIZE ? ARES_RESULT_PERMERROR : + ves == PDKIM_VERIFY_INVALID_PUBKEY_DNSRECORD ? ARES_RESULT_PERMERROR : + ves == PDKIM_VERIFY_INVALID_PUBKEY_IMPORT ? ARES_RESULT_PERMERROR : + ARES_RESULT_UNKNOWN : + ARES_RESULT_UNKNOWN; + dkim_history_buffer = string_sprintf("%sdkim %s %d\n", dkim_history_buffer, + sig->domain, dkim_ares_result); + sig = sig->next; + } + libdm_status = opendmarc_policy_query_dmarc(dmarc_pctx, US""); + switch (libdm_status) + { + case DMARC_DNS_ERROR_NXDOMAIN: + case DMARC_DNS_ERROR_NO_RECORD: + DEBUG(D_receive) + debug_printf("DMARC no record found for %s\n", header_from_sender); + has_dmarc_record = FALSE; + break; + case DMARC_PARSE_OKAY: + DEBUG(D_receive) + debug_printf("DMARC record found for %s\n", header_from_sender); + break; + case DMARC_PARSE_ERROR_BAD_VALUE: + DEBUG(D_receive) + debug_printf("DMARC record parse error for %s\n", header_from_sender); + has_dmarc_record = FALSE; + break; + default: + /* everything else, skip dmarc */ + DEBUG(D_receive) + debug_printf("DMARC skipping (%d), unsure what to do with %s", + libdm_status, from_header->text); + has_dmarc_record = FALSE; + break; + } + +/* Store the policy string in an expandable variable. */ + + libdm_status = opendmarc_policy_fetch_p(dmarc_pctx, &tmp_ans); + for (c = 0; dmarc_policy_description[c].name; c++) + if (tmp_ans == dmarc_policy_description[c].value) + { + dmarc_domain_policy = string_sprintf("%s",dmarc_policy_description[c].name); + break; + } + + /* Can't use exim's string manipulation functions so allocate memory + for libopendmarc using its max hostname length definition. */ + + dmarc_domain = US calloc(DMARC_MAXHOSTNAMELEN, sizeof(uschar)); + libdm_status = opendmarc_policy_fetch_utilized_domain(dmarc_pctx, + dmarc_domain, DMARC_MAXHOSTNAMELEN-1); + dmarc_used_domain = string_copy(dmarc_domain); + free(dmarc_domain); + + if (libdm_status != DMARC_PARSE_OKAY) + log_write(0, LOG_MAIN|LOG_PANIC, + "failure to read domainname used for DMARC lookup: %s", + opendmarc_policy_status_to_str(libdm_status)); + + dmarc_policy = libdm_status = opendmarc_get_policy_to_enforce(dmarc_pctx); + switch(libdm_status) + { + case DMARC_POLICY_ABSENT: /* No DMARC record found */ + dmarc_status = US"norecord"; + dmarc_pass_fail = US"none"; + dmarc_status_text = US"No DMARC record"; + action = DMARC_RESULT_ACCEPT; + break; + case DMARC_FROM_DOMAIN_ABSENT: /* No From: domain */ + dmarc_status = US"nofrom"; + dmarc_pass_fail = US"temperror"; + dmarc_status_text = US"No From: domain found"; + action = DMARC_RESULT_ACCEPT; + break; + case DMARC_POLICY_NONE: /* Accept and report */ + dmarc_status = US"none"; + dmarc_pass_fail = US"none"; + dmarc_status_text = US"None, Accept"; + action = DMARC_RESULT_ACCEPT; + break; + case DMARC_POLICY_PASS: /* Explicit accept */ + dmarc_status = US"accept"; + dmarc_pass_fail = US"pass"; + dmarc_status_text = US"Accept"; + action = DMARC_RESULT_ACCEPT; + break; + case DMARC_POLICY_REJECT: /* Explicit reject */ + dmarc_status = US"reject"; + dmarc_pass_fail = US"fail"; + dmarc_status_text = US"Reject"; + action = DMARC_RESULT_REJECT; + break; + case DMARC_POLICY_QUARANTINE: /* Explicit quarantine */ + dmarc_status = US"quarantine"; + dmarc_pass_fail = US"fail"; + dmarc_status_text = US"Quarantine"; + action = DMARC_RESULT_QUARANTINE; + break; + default: + dmarc_status = US"temperror"; + dmarc_pass_fail = US"temperror"; + dmarc_status_text = US"Internal Policy Error"; + action = DMARC_RESULT_TEMPFAIL; + break; + } + + libdm_status = opendmarc_policy_fetch_alignment(dmarc_pctx, &da, &sa); + if (libdm_status != DMARC_PARSE_OKAY) + log_write(0, LOG_MAIN|LOG_PANIC, "failure to read DMARC alignment: %s", + opendmarc_policy_status_to_str(libdm_status)); + + if (has_dmarc_record) + { + log_write(0, LOG_MAIN, "DMARC results: spf_domain=%s dmarc_domain=%s " + "spf_align=%s dkim_align=%s enforcement='%s'", + spf_sender_domain, dmarc_used_domain, + sa==DMARC_POLICY_SPF_ALIGNMENT_PASS ?"yes":"no", + da==DMARC_POLICY_DKIM_ALIGNMENT_PASS ?"yes":"no", + dmarc_status_text); + history_file_status = dmarc_write_history_file(); + /* Now get the forensic reporting addresses, if any */ + ruf = opendmarc_policy_fetch_ruf(dmarc_pctx, NULL, 0, 1); + dmarc_send_forensic_report(ruf); + } + } + +/* shut down libopendmarc */ +if (dmarc_pctx) + (void) opendmarc_policy_connect_shutdown(dmarc_pctx); +if (!f.dmarc_disable_verify) + (void) opendmarc_policy_library_shutdown(&dmarc_ctx); + +return OK; +} + +static int +dmarc_write_history_file() +{ +int history_file_fd; +ssize_t written_len; +int tmp_ans; +u_char **rua; /* aggregate report addressees */ +uschar *history_buffer = NULL; + +if (!dmarc_history_file) + { + DEBUG(D_receive) debug_printf("DMARC history file not set\n"); + return DMARC_HIST_DISABLED; + } +history_file_fd = log_create(dmarc_history_file); + +if (history_file_fd < 0) + { + log_write(0, LOG_MAIN|LOG_PANIC, "failure to create DMARC history file: %s", + dmarc_history_file); + return DMARC_HIST_FILE_ERR; + } + +/* Generate the contents of the history file */ +history_buffer = string_sprintf( + "job %s\nreporter %s\nreceived %ld\nipaddr %s\nfrom %s\nmfrom %s\n", + message_id, primary_hostname, time(NULL), sender_host_address, + header_from_sender, expand_string(US"$sender_address_domain")); + +if (spf_response) + history_buffer = string_sprintf("%sspf %d\n", history_buffer, dmarc_spf_ares_result); + /* history_buffer = string_sprintf("%sspf -1\n", history_buffer); */ + +history_buffer = string_sprintf( + "%s%spdomain %s\npolicy %d\n", + history_buffer, dkim_history_buffer, dmarc_used_domain, dmarc_policy); + +if ((rua = opendmarc_policy_fetch_rua(dmarc_pctx, NULL, 0, 1))) + for (tmp_ans = 0; rua[tmp_ans]; tmp_ans++) + history_buffer = string_sprintf("%srua %s\n", history_buffer, rua[tmp_ans]); +else + history_buffer = string_sprintf("%srua -\n", history_buffer); + +opendmarc_policy_fetch_pct(dmarc_pctx, &tmp_ans); +history_buffer = string_sprintf("%spct %d\n", history_buffer, tmp_ans); + +opendmarc_policy_fetch_adkim(dmarc_pctx, &tmp_ans); +history_buffer = string_sprintf("%sadkim %d\n", history_buffer, tmp_ans); + +opendmarc_policy_fetch_aspf(dmarc_pctx, &tmp_ans); +history_buffer = string_sprintf("%saspf %d\n", history_buffer, tmp_ans); + +opendmarc_policy_fetch_p(dmarc_pctx, &tmp_ans); +history_buffer = string_sprintf("%sp %d\n", history_buffer, tmp_ans); + +opendmarc_policy_fetch_sp(dmarc_pctx, &tmp_ans); +history_buffer = string_sprintf("%ssp %d\n", history_buffer, tmp_ans); + +history_buffer = string_sprintf( + "%salign_dkim %d\nalign_spf %d\naction %d\n", + history_buffer, da, sa, action); + +/* Write the contents to the history file */ +DEBUG(D_receive) + debug_printf("DMARC logging history data for opendmarc reporting%s\n", + (host_checking || f.running_in_test_harness) ? " (not really)" : ""); +if (host_checking || f.running_in_test_harness) + { + DEBUG(D_receive) + debug_printf("DMARC history data for debugging:\n%s", history_buffer); + } +else + { + written_len = write_to_fd_buf(history_file_fd, + history_buffer, + Ustrlen(history_buffer)); + if (written_len == 0) + { + log_write(0, LOG_MAIN|LOG_PANIC, "failure to write to DMARC history file: %s", + dmarc_history_file); + return DMARC_HIST_WRITE_ERR; + } + (void)close(history_file_fd); + } +return DMARC_HIST_OK; +} + + +uschar * +dmarc_exim_expand_query(int what) +{ +if (f.dmarc_disable_verify || !dmarc_pctx) + return dmarc_exim_expand_defaults(what); + +if (what == DMARC_VERIFY_STATUS) + return dmarc_status; +return US""; +} + +uschar * +dmarc_exim_expand_defaults(int what) +{ +if (what == DMARC_VERIFY_STATUS) + return f.dmarc_disable_verify ? US"off" : US"none"; +return US""; +} + + +gstring * +authres_dmarc(gstring * g) +{ +if (f.dmarc_has_been_checked) + { + g = string_append(g, 2, US";\n\tdmarc=", dmarc_pass_fail); + if (header_from_sender) + g = string_append(g, 2, US" header.from=", header_from_sender); + } +return g; +} + +# endif /* SUPPORT_SPF */ +#endif /* EXPERIMENTAL_DMARC */ +/* vi: aw ai sw=2 + */ |